If the Earth Were to Warm Up a Bit, What

If the Earth were to warm up a bit, what would happen?

A) Carbonate materials would form in the oceans more rapidly, the atmospheric CO₂ content would decrease, and the greenhouse effect would weaken.
B) Carbonate materials would form in the oceans more slowly, the atmospheric CO₂ content would increase, and the greenhouse effect would strengthen.
C) Carbonate materials would form in the oceans more rapidly, the atmospheric CO₂ content would decrease, and the greenhouse effect would strengthen.
D) There would be a runaway greenhouse effect, with the Earth becoming ever hotter until the oceans evaporated (as may have happened on Venus) .
E) The ice caps would melt and cool the Earth back to its normal temperature.